Blue Sea Systems 187-Series Switchable Thermal Circuit Breaker, 48V DC, Type III, Trip-Free, Ignition Protected
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Overview
The Blue Sea Systems 187-Series is a switchable thermal circuit breaker for DC marine circuits where circuit protection and a manual reset switch need to sit in the same accessible device. This 48V DC breaker family covers amperage ratings from 25A to 200A, with panel-mount and surface-mount versions for different electrical layouts on board.
Each breaker uses a thermally responsive bi-metal blade and Type III switchable manual-reset operation. The trip-free mechanism means the lever cannot be held closed against a fault, which matters on battery feeds, windlass circuits, inverter feeds, charging circuits, and other DC loads where fault current needs to be interrupted safely.
The range uses 5/16 inch-18 terminal studs, accepts #10 or M5 mounting screws, and has published interrupt ratings of 5000A at 14V DC, 3000A at 28V DC, and 1500A at 48V DC. The operating temperature range is -40 C to 85 C, giving it room for engine room heat, exposed lockers, and colder storage conditions.
Key features
- Combines DC circuit protection and manual switching in one breaker for circuits that need accessible shutoff and reset.
- 48V DC maximum voltage rating, with amperage options from 25A to 200A across the range.
- Type III switchable manual-reset operation with a trip-free mechanism that cannot be held closed during a fault.
- Panel-mount and surface-mount configurations support different helm panels, electrical lockers, battery compartments, and distribution layouts.
- 5/16 inch-18 terminal studs give high-current cable lugs a secure termination point.
- Large clearance around the terminal studs helps accommodate heavy gauge wire lugs used on higher-amperage DC circuits.
- Interrupt capacity is rated at 5000A at 14V DC, 3000A at 28V DC, and 1500A at 48V DC.
- Ignition protected to SAE J1171 for installation aboard gasoline-powered boats.
- Thermoset polyester case material supports use in demanding marine electrical spaces.
Variants
This range varies by mounting style and amperage. The available configurations include panel-mount and surface-mount versions, with ratings from 25A through 200A to match the protected circuit and the cable size selected for the installation.
The breaker family remains a 48V DC switchable thermal breaker with manual reset and trip-free operation across the range. Select the mounting format that matches the physical location of the breaker, then match the amperage to the circuit protection requirements of the equipment and wiring.
Installation and setup
Panel-mount versions suit installations where the breaker face is intended to be visible and reachable through a panel. Surface-mount versions are useful where the breaker needs to be installed directly onto a bulkhead, backing board, or electrical mounting surface without building it into a finished panel.
The breaker should be placed where the lever can be reached for reset and isolation, while keeping cable runs practical and protected. As with any high-current DC circuit, the breaker rating must be coordinated with the conductor size, expected load, voltage drop plan, and the equipment manufacturer’s requirements.
Electrical and system integration
The 187-Series is commonly used in DC distribution where a fuse alone is less convenient because the circuit also benefits from a visible lever and manual reset. The lever gives a clear indication of breaker status and allows the circuit to be opened for service without removing a fuse.
For circuits with heavy startup current, confirm the breaker rating and trip behavior against the load profile before installation. Motors, windlasses, pumps, chargers, and inverter circuits can draw inrush current that needs to be considered during circuit protection planning.
Use cases on board
This breaker family is a practical match for boat owners, technicians, and builders working on DC electrical systems that need serviceable protection in a compact mounting footprint. It fits well in battery compartments, DC distribution panels, equipment lockers, and other locations where a resettable breaker is easier to manage than replacing a fuse.
Shipping
We ship worldwide from the United States. Rates are calculated at checkout based on destination and package weight. Some items include free shipping, which will show automatically. Not every product is eligible for international shipping; checkout will confirm eligibility. We do not ship to PO Boxes except through USPS, and not all packages qualify.
Processing and dispatch
Most orders are verified, packed, and handed to the carrier within 1 to 2 business days. Some products may need extra handling time or ship directly from the manufacturer. For certain international orders, inventory transfers between warehouses may add time. If any delay is expected, we will let you know the dispatch date.
Delivery and tracking
Deliveries are handled by trusted carriers such as USPS, UPS, FedEx, and DHL. Estimated arrival times appear at checkout and depend on your location and the service you choose. These are estimates and can be affected by customs or carrier disruptions. A shipping confirmation with a tracking link is emailed when your order ships, and tracking may take up to 24 hours to update. You can also view tracking in your account.
Duties, taxes, and support
International customers are responsible for any customs duties, taxes, and fees charged by the destination country. If these charges are refused and a shipment returns to us, the carrier’s return cost and any re-entry customs fees will be deducted from the refund. If your order is late or you need help, contact cs@qualityboatparts.com and we will assist you.
Quality Boat Parts is a reseller. Many items include a manufacturer’s warranty, and all warranty service is handled directly by the manufacturer. We do not manage or administer warranty claims on behalf of customers.
Warranty terms, coverage, and duration are set by each manufacturer. Issues involving defects, repairs, or replacements must be addressed with the manufacturer’s support team. When available, the warranty period is listed on the product page. If it is not shown, contact us or the manufacturer for details before purchasing.
To start a claim, the customer must contact the manufacturer and follow their process. Keep your proof of purchase and original packaging, and register the product if the manufacturer requires it, as these are often needed for warranty service.
We are happy to help you find the right contact or documentation, but we cannot decide outcomes or intervene in claim resolutions. For guidance, email cs@qualityboatparts.com.